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Message-ID: <AANLkTinZmv540r+EkjwUu6cd9c1u7qG9iR+pvp3YqZC1@mail.gmail.com>
Date: Tue, 23 Nov 2010 16:40:03 +0900
From: Minchan Kim <minchan.kim@...il.com>
To: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
linux-mm <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>,
Peter Zijlstra <peterz@...radead.org>,
Rik van Riel <riel@...hat.com>,
Johannes Weiner <hannes@...xchg.org>,
Nick Piggin <npiggin@...nel.dk>
Subject: Re: [RFC 1/2] deactive invalidated pages
Hi KOSAKI,
2010/11/23 KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>:
>> By Other approach, app developer uses POSIX_FADV_DONTNEED.
>> But it has a problem. If kernel meets page is writing
>> during invalidate_mapping_pages, it can't work.
>> It is very hard for application programmer to use it.
>> Because they always have to sync data before calling
>> fadivse(..POSIX_FADV_DONTNEED) to make sure the pages could
>> be discardable. At last, they can't use deferred write of kernel
>> so that they could see performance loss.
>> (http://insights.oetiker.ch/linux/fadvise.html)
>
> If rsync use the above url patch, we don't need your patch.
> fdatasync() + POSIX_FADV_DONTNEED should work fine.
It works well. But it needs always fdatasync before calling fadvise.
For small file, it hurt performance since we can't use the deferred write.
>
> So, I think the core worth of previous PeterZ's patch is in readahead
> based heuristics. I'm curious why you drop it.
>
In previous peter's patch, it couldn't move active page into inactive list.
So it's not what i want and I think invalidation is stronger hint than
the readahead heuristic.
But if we need it, I will add it in my series. It can help reclaiming
unnecessary inactive page asap.
but before that, I hope we make sure fadvise works well enough.
>
>> In fact, invalidate is very big hint to reclaimer.
>> It means we don't use the page any more. So let's move
>> the writing page into inactive list's head.
>
> But, I agree this.
Thank you.
>
>
>>
>> If it is real working set, it could have a enough time to
>> activate the page since we always try to keep many pages in
>> inactive list.
>>
>> I reuse lru_demote of Peter with some change.
>>
>> Reported-by: Ben Gamari <bgamari.foss@...il.com>
>> Signed-off-by: Minchan Kim <minchan.kim@...il.com>
>> Signed-off-by: Peter Zijlstra <peterz@...radead.org>
>> Cc: Rik van Riel <riel@...hat.com>
>> Cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
>> Cc: Johannes Weiner <hannes@...xchg.org>
>> Cc: Nick Piggin <npiggin@...nel.dk>
>>
>> Ben, Remain thing is to modify rsync and use
>> fadvise(POSIX_FADV_DONTNEED). Could you test it?
>> ---
>> include/linux/swap.h | 1 +
>> mm/swap.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++
>> mm/truncate.c | 11 +++++---
>> 3 files changed, 69 insertions(+), 4 deletions(-)
>>
>> diff --git a/include/linux/swap.h b/include/linux/swap.h
>> index eba53e7..a3c9248 100644
>> --- a/include/linux/swap.h
>> +++ b/include/linux/swap.h
>> @@ -213,6 +213,7 @@ extern void mark_page_accessed(struct page *);
>> extern void lru_add_drain(void);
>> extern int lru_add_drain_all(void);
>> extern void rotate_reclaimable_page(struct page *page);
>> +extern void lru_deactive_page(struct page *page);
>> extern void swap_setup(void);
>>
>> extern void add_page_to_unevictable_list(struct page *page);
>> diff --git a/mm/swap.c b/mm/swap.c
>> index 3f48542..56fa298 100644
>> --- a/mm/swap.c
>> +++ b/mm/swap.c
>> @@ -39,6 +39,8 @@ int page_cluster;
>>
>> static DEFINE_PER_CPU(struct pagevec[NR_LRU_LISTS], lru_add_pvecs);
>> static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs);
>> +static DEFINE_PER_CPU(struct pagevec, lru_deactive_pvecs);
>> +
>>
>> /*
>> * This path almost never happens for VM activity - pages are normally
>> @@ -266,6 +268,45 @@ void add_page_to_unevictable_list(struct page *page)
>> spin_unlock_irq(&zone->lru_lock);
>> }
>>
>> +static void __pagevec_lru_deactive(struct pagevec *pvec)
>> +{
>> + int i, lru, file;
>> +
>> + struct zone *zone = NULL;
>> +
>> + for (i = 0; i < pagevec_count(pvec); i++) {
>> + struct page *page = pvec->pages[i];
>> + struct zone *pagezone = page_zone(page);
>> +
>> + if (pagezone != zone) {
>> + if (zone)
>> + spin_unlock_irq(&zone->lru_lock);
>> + zone = pagezone;
>> + spin_lock_irq(&zone->lru_lock);
>> + }
>> +
>> + if (PageLRU(page)) {
>> + if (PageActive(page)) {
>> + file = page_is_file_cache(page);
>> + lru = page_lru_base_type(page);
>> + del_page_from_lru_list(zone, page,
>> + lru + LRU_ACTIVE);
>> + ClearPageActive(page);
>> + ClearPageReferenced(page);
>> + add_page_to_lru_list(zone, page, lru);
>> + __count_vm_event(PGDEACTIVATE);
>> +
>> + update_page_reclaim_stat(zone, page, file, 0);
>
> When PageActive is unset, we need to change cgroup lru too.
Doesn't add_page_to_lru_list/del_page_from_lru_list do it?
>
>
>> + }
>> + }
>> + }
>> + if (zone)
>> + spin_unlock_irq(&zone->lru_lock);
>> +
>> + release_pages(pvec->pages, pvec->nr, pvec->cold);
>> + pagevec_reinit(pvec);
>> +}
>> +
>> /*
>> * Drain pages out of the cpu's pagevecs.
>> * Either "cpu" is the current CPU, and preemption has already been
>> @@ -292,8 +333,28 @@ static void drain_cpu_pagevecs(int cpu)
>> pagevec_move_tail(pvec);
>> local_irq_restore(flags);
>> }
>> +
>> + pvec = &per_cpu(lru_deactive_pvecs, cpu);
>> + if (pagevec_count(pvec))
>> + __pagevec_lru_deactive(pvec);
>> +}
>> +
>> +/*
>> + * Function used to forecefully demote a page to the head of the inactive
>> + * list.
>> + */
>> +void lru_deactive_page(struct page *page)
>> +{
>> + if (likely(get_page_unless_zero(page))) {
>
> Probably, we can check PageLRU and PageActive here too. It help to avoid
> unnecessary batching and may slightly increase performance.
Yes. Thanks. Will fix.
>
>
>> + struct pagevec *pvec = &get_cpu_var(lru_deactive_pvecs);
>> +
>> + if (!pagevec_add(pvec, page))
>> + __pagevec_lru_deactive(pvec);
>> + put_cpu_var(lru_deactive_pvecs);
>> + }
>> }
>>
>> +
>> void lru_add_drain(void)
>> {
>> drain_cpu_pagevecs(get_cpu());
>> diff --git a/mm/truncate.c b/mm/truncate.c
>> index cd94607..c73fb19 100644
>> --- a/mm/truncate.c
>> +++ b/mm/truncate.c
>> @@ -332,7 +332,8 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping,
>> {
>> struct pagevec pvec;
>> pgoff_t next = start;
>> - unsigned long ret = 0;
>> + unsigned long ret;
>> + unsigned long count = 0;
>> int i;
>>
>> pagevec_init(&pvec, 0);
>> @@ -359,8 +360,10 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping,
>> if (lock_failed)
>> continue;
>>
>> - ret += invalidate_inode_page(page);
>> -
>> + ret = invalidate_inode_page(page);
>> + if (!ret)
>> + lru_deactive_page(page);
>> + count += ret;
>> unlock_page(page);
>> if (next > end)
>> break;
>> @@ -369,7 +372,7 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping,
>> mem_cgroup_uncharge_end();
>> cond_resched();
>> }
>> - return ret;
>> + return count;
>> }
>> EXPORT_SYMBOL(invalidate_mapping_pages);
>>
>> --
>> 1.7.0.4
>>
>> --
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>
>
>
>
--
Kind regards,
Minchan Kim
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